What inspires two actors to take four months out of their careers to travel across some of the most remote parts of the world on motorbikes?

Mishal Husain asked Ewan McGregor (better known to movie audiences as the young Obi-Wan Kenobi) and Charley Boorman (star of the movie The Emerald Forest and son of the legendary director Sir John Boorman) why they decided to travel from London to New York the long way round.

Ewan explained that the trip was born purely out of "our desire to ride motorbikes for a very long time".

The two men met on a film set and immediately bonded over their love of bikes. A dream trip like this was just a natural extension of that.

The two started their journey in London in April 2004, and crossed over to mainland Europe.

They then travelled France, Belgium, Germany, Czech Republic, Slovakia, Ukraine, Russia, Kazakhstan, Mongolia, Siberia, Alaska before riding into New York City┐s Battery Park in late July.

Falling off

Their journey took them across some of the world┐s most remote areas as they crossed the border into Mongolia, roads became tracks and distances measured in hours┐ travel.

Falling off their bikes became part and parcel of the trip. "I think we started counting how many times we fell off in the first week," explained Charley, "and then we gave up because we did fall a lot."

I felt that there was such generosity shown towards us across the way

Ewan McGregor

But there was little doubt that travelling by bike allowed the two friends to see far more of the country they were covering.

"The thing about riding a bike as opposed to being in a car is that you're really part of the landscape on a motorcycle and you travel slowly across, the landscape changes round about you and you become more part of it as a result," Ewan told the programme.

The pair described Mongolia as one of the highlights of the trip, "the furthest away from our culture that we witnessed."

Being recognised

Travelling on large bikes and with a cameraman on board, the actor pair weren't exactly inconspicuous, and they did encounter some media interest.

They described waiting at the Ukrainian border for fourteen hours signing autographs before being allowed to pass through.

Ewan recalled a "terrifying" incident in Kazakhstan where he and Charley were held at gunpoint by a man in a car - who then laughed and drove off. But overall, the reception they faced was very warm.

"I felt that there was such generosity shown towards us across the way, and interest, and we represented to people maybe in some of the smaller towns in Siberia .. a kind of freedom to those people."

The project which began as two friends making an epic journey snowballed - the whole trip was filmed and has now become a documentary and a book.

But Ewan McGregor and Charley Boorman agree that the experience was everything they'd hoped for - two best friends on their motorbikes, travelling across the world.

HARDtalk Extra can be seen on Fridays on BBC World at 03:30 GMT, 08:30 GMT, 11:30 GMT, 15:30 GMT, 18:30 GMT and 23:30 GMT